grep From STDIN

grep from STDIN

So far you have only used grep to search a specific file. However, you can pass input directly to grep and match STDIN results against a Regular Expression pattern.

ls | grep Example

Match patterns for all contents of the home directory:

Match all files with a . in our home directory.

ls ~ | grep '\.'

Output:

ls to grep output

Note

The . is a Regular Expression special symbol meaning to match any character. In order to search for an actual . you need to escape the . so that RegEx knows that you are searching for an actual period and not referencing special symbol. The escape special symbol in RegEx is the backslash \ symbol.

When you provide the regular expression: '\.' you are telling grep to match any lines that have a . in them.

history | grep Example

Match all grep commands in our bash history

history | grep 'grep'

Output:

history to grep ‘\.’ output

find | grep Example

Match all /bin/ for files containing the word bash in the root directory.

sudo find / -name 'bash' | grep '/bin/'

Output:

find to grep output

curl | grep Example

Send a curl request directly to the API and match the results (csv in STDIN) to a specific pattern.

curl -s https://launchcodetechnicaltraining.org/api/walkthrough/user?data_format=csv | grep 'Microsoft$'

Output:

curl to grep output